A Relay Node (RN) is introduced to a Long Term Evolution-Advanced (LTE-A) system for increased network coverage, where the RN is connected with a Donor evolved Node B (DeNB) by a wireless network. The RN can further be applied to a railway and other mobile environments at a high speed to thereby lower the number of times that a User Equipment (UE) is handed over, to improve the quality of a signal in a carriage and other purposes.
FIG. 1 illustrates the network architecture of the LTE-A system with RN deployed in the prior art, where the RN accesses to an Evolved Packet Core (EPC) via a donor cell of the DeNB, while there is no wired interface between the RN and the EPC, and each RN can control one or more cells. In this architecture, an interface between the UE and the RN is referred to Uu interface, and an interface between the RN and the DeNB is referred to Un interface, where the DeNB is integrated with a part of a Serving Gateway/Packet Data Network Gateway (SGW/PGW) function. The RN includes a stationary RN and a mobile RN, where a relay node of which the location is unchanged is referred to stationary RN and a relay node which supports mobility is referred a mobile RN.
For the stationary RN, the stationary RN is served by the DeNB with the necessary SGW/PGW function. The DeNB transmits the Internet Protocol (IP) address of the SGW/PGW function integrated therewith to a Mobility Management Entity (MME) of the stationary RN, and after the RN is authenticated successfully, the MME selects the DeNB as a SGW/PGW of the RN according to the received IP address and sets up an S5 interface between the MME and the DeNB, and in the meantime the DeNB serves as an eNB of the stationary RN and there is a further S1-C interface between the DeNB and the MME of the stationary RN, as illustrated in FIG. 2.
For the mobile RN, the MME selects a Mobility Anchor as an SGW/PGW of the mobile RN and sets up an S5 interface between the MME and the mobility anchor. When accessing the network, the Mobility Anchor sets up an S1-C interface between the MME of the mobile RN and the Mobility Anchor in a manner of eNB, and when the mobile RN is handed over to another DeNB, the mobile RN only has the serving eNB (i.e., the DeNB) changed, the MME of the mobile RN sets up an S1-C signaling connection between the MME and the destination DeNB, and the mobility anchor transfers an S1-U tunnel borne by an Evolved Packet System (EPS) of the mobile RN from the source DeNB to the destination DeNB, as illustrated in FIG. 2.
In summary, the specification in the prior art only relates to how the DeNB assists the MME in selecting an SGW/PGW for the stationary RN when the stationary RN accesses the network, but doesn't relate to how the DeNB assists the MME in selecting a mobility anchor as an SGW/PGW for the mobile RN when the mobile RN accesses the network.